Eric B. Searle

Positive biodiversity-productivity relationship predominant in global forests.

Global biodiversity and productivity The relationship between biodiversity and ecosystem productivity has been explored in detail in herbaceous vegetation, but patterns in forests are far less well understood. Liang et al. have amassed a global forest data set from >770,000 sample plots in 44 countries. A positive and consistent relationship can be discerned between tree diversity and ecosystem productivity at landscape, country, and ecoregion scales. On average, a 10% loss in biodiversity leads to a 3% loss in productivity. This means that the economic value of maintaining biodiversity for the sake of global forest productivity is more than fivefold greater than global conservation costs. Science, this issue p. 196 Global forest inventory records suggest that biodiversity loss would result in a decline in forest productivity worldwide. INTRODUCTION The biodiversity-productivity relationship (BPR; the effect of biodiversity on ecosystem productivity) is foundational to our understanding of the global extinction crisis and its impacts on the functioning of natural ecosystems. The BPR has been a prominent research topic within ecology in recent decades, but it is only recently that we have begun to develop a global perspective. RATIONALE Forests are the most important global repositories of terrestrial biodiversity, but deforestation, forest degradation, climate change, and other factors are threatening approximately one half of tree species worldwide. Although there have been substantial efforts to strengthen the preservation and sustainable use of forest biodiversity throughout the globe, the consequences of this diversity loss pose a major uncertainty for ongoing international forest management and conservation efforts. The forest BPR represents a critical missing link for accurate valuation of global biodiversity and successful integration of biological conservation and socioeconomic development. Until now, there have been limited tree-based diversity experiments, and the forest BPR has only been explored within regional-scale observational studies. Thus, the strength and spatial variability of this relationship remains unexplored at a global scale. RESULTS We explored the effect of tree species richness on tree volume productivity at the global scale using repeated forest inventories from 777,126 permanent sample plots in 44 countries containing more than 30 million trees from 8737 species spanning most of the global terrestrial biomes. Our findings reveal a consistent positive concave-down effect of biodiversity on forest productivity across the world, showing that a continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The BPR shows considerable geospatial variation across the world. The same percentage of biodiversity loss would lead to a greater relative (that is, percentage) productivity decline in the boreal forests of North America, Northeastern Europe, Central Siberia, East Asia, and scattered regions of South-central Africa and South-central Asia. In the Amazon, West and Southeastern Africa, Southern China, Myanmar, Nepal, and the Malay Archipelago, however, the same percentage of biodiversity loss would lead to greater absolute productivity decline. CONCLUSION Our findings highlight the negative effect of biodiversity loss on forest productivity and the potential benefits from the transition of monocultures to mixed-species stands in forestry practices. The BPR we discover across forest ecosystems worldwide corresponds well with recent theoretical advances, as well as with experimental and observational studies on forest and nonforest ecosystems. On the basis of this relationship, the ongoing species loss in forest ecosystems worldwide could substantially reduce forest productivity and thereby forest carbon absorption rate to compromise the global forest carbon sink. We further estimate that the economic value of biodiversity in maintaining commercial forest productivity alone is

Persistent and pervasive compositional shifts of western boreal forest plots in Canada

166 billion to

Phosphorus amendment mitigates nitrogen addition-induced phosphorus limitation in two plant species in a desert steppe, China

490 billion per year. Although representing only a small percentage of the total value of biodiversity, this value is two to six times as much as it would cost to effectively implement conservation globally. These results highlight the necessity to reassess biodiversity valuation and the potential benefits of integrating and promoting biological conservation in forest resource management and forestry practices worldwide. Global effect of tree species diversity on forest productivity. Ground-sourced data from 777,126 global forest biodiversity permanent sample plots (dark blue dots, left), which cover a substantial portion of the global forest extent (white), reveal a consistent positive and concave-down biodiversity-productivity relationship across forests worldwide (red line with pink bands representing 95% confidence interval, right). The biodiversity-productivity relationship (BPR) is foundational to our understanding of the global extinction crisis and its impacts on ecosystem functioning. Understanding BPR is critical for the accurate valuation and effective conservation of biodiversity. Using ground-sourced data from 777,126 permanent plots, spanning 44 countries and most terrestrial biomes, we reveal a globally consistent positive concave-down BPR, showing that continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The value of biodiversity in maintaining commercial forest productivity alone—US

Biodiversity as a solution to mitigate climate change impacts on the functioning of forest ecosystems

166 billion to 490 billion per year according to our estimation—is more than twice what it would cost to implement effective global conservation. This highlights the need for a worldwide reassessment of biodiversity values, forest management strategies, and conservation priorities.

Climate change-associated trends in biomass dynamics are consistent across soil drainage classes in western boreal forests of Canada

Species compositional shifts have important consequences to biodiversity and ecosystem function and services to humanity. In boreal forests, compositional shifts from late-successional conifers to early-successional conifers and deciduous broadleaves have been postulated based on increased fire frequency associated with climate change truncating stand age-dependent succession. However, little is known about how climate change has affected forest composition in the background between successive catastrophic fires in boreal forests. Using 1797 permanent sample plots from western boreal forests of Canada measured from 1958 to 2013, we show that after accounting for stand age-dependent succession, the relative abundances of early-successional deciduous broadleaves and early-successional conifers have increased at the expense of late-successional conifers with climate change. These background compositional shifts are persistent temporally, consistent across all forest stand ages and pervasive spatially across the region. Rising atmospheric CO2 promoted early-successional conifers and deciduous broadleaves, and warming increased early-successional conifers at the expense of late-successional conifers, but compositional shifts were not associated with climate moisture index. Our results emphasize the importance of climate change on background compositional shifts in the boreal forest and suggest further compositional shifts as rising CO2 and warming will continue in the 21st century.

Climate change‐associated trends in net biomass change are age dependent in western boreal forests of Canada

Background and aimsThe increasing deposition of atmospheric nitrogen (N) due to anthropogenic activities has significantly enhanced N inputs to ecosystems, resulting in an imbalance in the N: phosphorus (P) ratios in plants and soils. This study aimed to determine whether, and to what extent, P addition alleviates N-induced P limitation in a desert steppe ecosystem.MethodsWe conducted a multi-level N:P supply experiment (i.e., constant N with varied P-addition levels) for a grass species, Pennisetum centrasiaticum, and a N-fixing species, Glycyrrhiza uralensis.ResultsWith increasing amounts of P addition (thereby decreasing the N:P ratio), green-leaf P concentrations of the two species studied tended to increase, while P-resorption proficiency and efficiency tended to decrease. There were no consistent trends in green-leaf N concentrations in response to P addition. However, both species exhibited high N-resorption proficiency, especially in G. uralensis, with high P addition. Generally, the carbon (C):P and N:P ratios both in soils and in green leaves had positive relationships with green-leaf N concentration and P-resorption proficiency of P. centrasiaticum as well as P-resorption traits of G. uralensis, but negative relationships with green-leaf P concentrations in both species.ConclusionsOur study indicates that P addition can alter P-conservation strategy and thereby releasing plant species from the N-induced imbalance of N:P ratios. However, large amounts of P addition could overcompensate and pose a risk of N limitation in desert steppe ecosystems.

Temporal changes in soil C‐N‐P stoichiometry over the past 60 years across subtropical China

Forest ecosystems are critical to mitigating greenhouse gas emissions through carbon sequestration. However, climate change has affected forest ecosystem functioning in both negative and positive ways, and has led to shifts in species/functional diversity and losses in plant species diversity which may impair the positive effects of diversity on ecosystem functioning. Biodiversity may mitigate climate change impacts on (I) biodiversity itself, as more‐diverse systems could be more resilient to climate change impacts, and (II) ecosystem functioning through the positive relationship between diversity and ecosystem functioning. By surveying the literature, we examined how climate change has affected forest ecosystem functioning and plant diversity. Based on the biodiversity effects on ecosystem functioning (B→EF), we specifically address the potential for biodiversity to mitigate climate change impacts on forest ecosystem functioning. For this purpose, we formulate a concept whereby biodiversity may reduce the negative impacts or enhance the positive impacts of climate change on ecosystem functioning. Further B→EF studies on climate change in natural forests are encouraged to elucidate how biodiversity might influence ecosystem functioning. This may be achieved through the detailed scrutiny of large spatial/long temporal scale data sets, such as long‐term forest inventories. Forest management strategies based on B→EF have strong potential for augmenting the effectiveness of the roles of forests in the mitigation of climate change impacts on ecosystem functioning.

Tree size thresholds produce biased estimates of forest biomass dynamics

BackgroundConsistent long-term declines in net aboveground biomass change have been reported in some boreal and tropical forests. Global change-type drought (i.e., demands of increased evapotranspiration exceeding soil water reserves) has been identified as the main driver for these declines. Despite the focus on reduced water availability, most studies relegate local site soil drainage to a plot random effect. However, if the major cause of some region’s recent loss in net aboveground biomass change is global change-type drought, those soils with less drainage capacity should help buffer against increased evapotranspiration, resulting in less negative effects of global change-type drought on growth, mortality and net biomass change.MethodsHere we used a network of 1279 permanent sampling plots, measured from 1958 to 2009, from western Canada, where long-term decline of climate moisture availability has been observed, to examine how soil drainage could affect the response of forest net biomass change and its components (growth and mortality) to global change-type drought.ResultsAfter accounting for the effects of endogenous forest age-related processes, temporal changes in absolute rates of biomass gain from growth did not differ among drainage classes, and temporal increases in biomass loss from tree mortality were also similar across drainage classes, resulting in similar decreases in net biomass change. Relative growth was significantly higher on moderately drained sites than well drained or poorly drained sites likely due to larger temporal decreases in standing biomass relative to declines in temporal growth on moderately drained soils. Moreover, growth, mortality, and net biomass change responded to atmospheric CO2, annual temperature anomaly, and standardized precipitation evapotranspiration index similarly across all drainage classes.ConclusionsOur results suggest that climate change serves as a top-down control on forest growth, mortality and net biomass change.